Extreme pressure lubricant



United States Patent Gil .ice

3,234,132 Patented Feb. 8, 1966 The present invention relates to diesters useful as synthetic lubricant additives. The diesters when added to synthetic lubricants provides the lubricants with improved extreme pressure properties.

The adidtives of the present invention can be identified by the following structural formula:

where X=O or S; Y=H or Cl, with the proviso that at least one of X and Y is S or Cl; R'is a divalent aliphatic hydrocarbon radical of up to 18 carbon atoms, preferably 8 to 16 carbon atoms when X is S and preferably 24 carbon atoms when Y is Cl and X is O. Preferably R: (CI-1 M wherein n is about 2 to 16. The additives are ordinarily of lubricating viscosity and compatible, i.e., soluble, miscible or dispersible with the synthetic fluids to which they are added.

The additive may be prepared by direct esterification 1 of chlorendic acid or its anhydride and the preferred agents are made from a chlorinated alcohol of 2 to 4 carbon atoms or an alkyl rnercaptan wlmre the alkyl group has 8 to 16 carbon atoms or by ester interchange between the ester of chlorendic acid and either the mercaptan or chlorinated alcohol. The preferred alkyl mercaptan contains 10-16 carbon atoms and particularly preferred is lauryl .mercaptan. The preferred chlorinated alcohol is ethylene chlorohydrin.

Whenthezreaction products are made by an ester interchange reaction, the esters of the chlorendic acid are employed. The esters may have the following structural formula:

01 H l Cl-C- CCOOR M 01-41-01 Cl JI in which R and R are lower alkyl radicals of, i.e., 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms. The esters used are those of the chlorendic acid and the lower aliphatic alcohols so that the alcohol produced in the reaction will be volatilized under the reaction conditions.

In preparing the reaction products of the present invention, a molar ratio of 0.5 to 2.0 moles of chlorendic acid, its anhydride or its ester per mole of the meroaptan or chlorinated alcohol is used. Preferably the molar ratio is 0.8 to 1.25:1; a particularly advantageous ratio being about 1:1. When the esterification reaction is conducted between chlorendic acid or its anhydride and the rnercaptan or chlorinated alcohol it is continued with concomitant boiling-off of water from the reaction mixture. The

COOR

temperature of this reaction is usually at least about 300 F. and should not be so high as to decompose the wanted product. If desired, the reaction can be conducted in the presence of a solvent, for instance an aromatic hydrocarbon such as xylene, and to provide a better reaction rate, I prefer to employ an acid esterification catalyst. Many of these catalysts are known and include for instance hydrochloric acid, sulfuric acid, aliphatic and aromatic sultonic acids, phosphoric acid, perchlor-ic acid, hydrobromic acid, hydrofluoric acid and dihydroxyfiuoboric acid. Other catalysts are thionyl chloride, boron trifiuoride, silicon tetrafluoride, the chlorides of magnesium, aluminum, iron, zinc, copper and tin and salts of mercury, silver, cobalt, nickel and cerium. In the preferred reaction, when employing chlorendic acid, I use about 0.1 to 0.5 weight percent of paratoluene suli'onic acid catalyst, a xylene solvent and a temperature or about 34-5 to 390 F. while boilin-g otf water by refluxing.

When employing the esterification or ester interchange alcoholysis reaction between the chlorendic acid ester and the 'rnercaptan or chlorinated alcohol, I prefer not to use a solvent and the temperature is generally above 350 F., but not so high as to decompose the wanted product. Advantageo-usly, the temperature is in the range of about 435 to 480 F. Many suitable ester exchange catalysts are known and include for instance, Zinc stearate, aluminum stearate, dibutyl-tin oxide, titanium tetraesters of lower aliphatic alcohols, sodium acid sulfate, sulfuric, hydrochloric and sulfon-ic acids, aluminum alkoxides, sodium methyl carbonate. Also, these catalysts are exemplified by the alkali metal and alkaline earth metal alkoxides, hydroxides and carbonates.

In both the direct and ester interchange reactions the reaction is continued with concomitant boiling-off of water (direct esterificat-ion) or alcohol (ester interchange) from the reaction mixture.

The additive or the present invention is incorporated in synthetic lubricants in amounts sufficient to endow the lubricant with improved load carrying capacities particularly as measured by the Falex Extreme Pressure Test. Normally about 0.5 to 20 weight percent, perterably about 1 to 10 weight percent of the diester is employed.

The synthetic fluids to which the reaction products of the present invention are added are esterebased oils of lubricating viscosity and may be for instance, a simple ester or compounds having multiple ester groupings such as complex esters, polyesters, or diesters. These esters are made from monoand polyhydroxy aliphatic alcohols and aliphatic carboxylic acids, frequently of about 4 to 12 carbon atoms; aliphatic including cycloaliphatic. The term alkanol is used to designate the monoand polyhyd-roxy alcohols while the term alkane canboxylic acid denotes the monoand polycanboxylic acids. The reaction acids. The reaction product of a monohydroxy all cohol and a monocarboxylic acid is usually considered .to be a simple ester. A diester is usually considered to be the reaction product of 1 rnole of a canboxylic acid, say of 6 to 10 carbon atoms, with 2 moles of a monohydric alcohol or of 1 mole of a glycol of 4 to 10 canbon atoms with two moles of a monocarboxylic acid of 4 to 10 carbon atoms. The die'ste-rs frequently contain from 20 to40 canbon atoms. One complex ester is of the X-YZY-X in which X represents a monohydric alcohol residue, Y represents a dicarboxylic acid residue and Z represents a glycol residue and the linkages are ester linkages. Those sents a glycol residue and Z represents a dibasic acid residue are also considered to be complex esters. The complex esters often have 30 to 50 carbon atoms. Polyesters, or polyester bright stocks can be prepared by direct esterification of dibasic acids with glycols in about equimolar quantities. The polyesterification reaction is usually continued until the product has a kinematic viscosity from about to 200 centistokes at 210 F., and preferably 40 to 130 centistokes at 210 F.

Although each of these. products in itself'is useful as a lubricant, they are particularly 7 useful when added or blended with each other in synthetic lubricant compositions.- These-esters and blends have been found to be especially adaptable to the conditions to which turbineengines are. exposed, since they can be [formulated to give a desirable combination of high flash point, low pour point, and high viscosity at elevated temperatures, and needcontain no additives which might leave aresidue upon volatilization. In addition, many complex esters have shown good stability to shear. Natural esters, such as castor oil may also beincluded in the blends, as may be up to about 1 percent or more by weight of a foam inhibitor suchas a methyl silicone polymer or other, additives to provide a particular characteristic, for instance,

extreme pressure or load carrying agents, corrosion inhibitors, etc., can be added. I

Typical synthetic lubricants may be formulated essentially from a major amount (about 60-85%) of a complex ester and a minor amount (about 15-40%) of :a.

diester, by stirring together a quantity of diester and com- .plexester at anele vated temperature, altering the. proportions of each component until the desired viscosity is reached. Polyesters can be employed to thicken diester base stocks to increase the load carrying capacityotf the base diester oil. The. polyester will generally 'notrcomprise more than about 50 weight percent of the blend, preferably about ,to 35 weight percent. Usually the amount of the polyester employed in any blend would be at least about 5 percent, and the majority of the lubricant,

is a diester. Other polymers such as acryloids may .be

added as thickeners to the esters, generally the simple.

esters such as the above diesters, to obtain a base oil of desired viscosity. The acryloids are'polymers of mixed C to C esters of methacrylic acid having 10,000 to 20,-

000 molecular weight. Advantageously the final lubri-t eating oil composition would have a maximum viscosity art-40 F. of about 13,000 centistokes and a minimum;

viscosity of about 7.5 centistokes at 210 F.

The monohydr ic alcohols employed inthese esters usually contain less than than about'20 carbon atoms and are generally aliphatic. Preferably the alcohol contains up to about 12 carbon atoms. Usefulaliphatic alcohols include butyl, hexyl, methyl, iso-octyl and dodecyl alcohols,

C 0x0 alcohols and octadecyl alcohols.- C to C1 branched chain primary alcohols are frequently used'to improve the low temperature viscosity of the finished 111-5 bricant composition. 'Alcoholssuch as n-decanol, 2-,ethyl-; hexanol, oxoalcohols, prepared by .the reaction of car-.

.bon monoxide .and hydrogen upon the olefins obtainable from petroleumproducts such as diisobutylene .and. .C-7 .oIefins, ether alcohols suchas'butyl canbitol, tripropylene glycol. mono-isopropyl ether, dipropylene glycol rnon0 q isopropyl ether, and products such as Tergitol 3A3, which has the formula C H O (CH CH O) H, are suitable alcohols for use to produce the desired lubricant. If the alcohol has no hydrogens on the beta carbon atoms,

it is; neo-structured; and esters of such alcohols areoften preferred. In particulan the nee-C alcohol-2,2,4 -trimethyl-pentanol-lgives lubricating diesters or complex esters suitable for blending with diesters to produce -Iubri-,

41 3,4-dimethylhexanol; 29%. 3,5-dimethylhexanol; 25%

4,5-dimethylhexanol; 1.4% 5.5-dimethylhexanol; 16%of a mixture of3-methylheptanoland S-e-thylheptanol; 2.3% 4'ethylhexanol; 4.3% a-alkyl alkanols and, 5% other materials.

Generally, the glycols contain from about 4 to 1-2 car-v bon atoms; however, if desired 7 they could contain a greater nuruber. Among the specific glycols which can be employed are 2-ethyl-l,3-hexanediol,. 2-jpropyl-3,3-hep-' tanediol, 2-methyl-l, 3-pentanediol; 2-butyl-1,3-butanebutanediol.

ular weight.

hexanediol. The 2,2-dimethyl glycols,-such as neopenty-l glycol-have been shown ,to impart; heat stability to the: 1

final blends. Minor amounts of other-glycols or other materials can be present as long as therdesired-properties.

ofthe product are not undulyldeleterious-ly affected! Aside from glycols, the esters-may be made from poly- I hydric alcohols, of more than two .hydroxyl groups, e.g., triand rtetrahydroxy. aliphatic alcoholsrhavin-g about 4 to 12 carbon atoms, preferably about 5 to 8 carbon atoms;

for instance pentaerythritol, trimethylolpropane .and the like.

ducted so as .to substantially completely esterify .the acids.

One, group of monocarboxylic acids includes those; of 8 to 24 carbon atoms such as stearic, lauric, etc. The .car- L boxylic acids employed in;making ester lubricants will I often contain from about4 to 12 carbon atoms. Suitable? acids are described in US. Patent No. 2,575,195 landinclude the. aliphatic dibasic acidsof branched or straight: chain structures which are saturated orunsaturated. The preferred acids are the saturated aliphatic carboxylic acids. 1

containing not more than about-.12 carbon atoms, and mixtures of theseracids. Such acids include @succinic,

adipic, suberic, 'azelaic and sebacic acids and isosebacic. acid when is a mixture of a-ethyl suberic acid, qt, oU-diethyL adipicacid and sebacic acid. This composite: of acids is attractive from the viewpoint of economy and availability. since it ,isimade from petroleum hydrocarbons rather than the natural oils and fatswhich are .used .in the manufaca ture of many. ether dicarboxyle acids, which natural oils and .fatsare frequently; in short supply. The preferred i diba'sic acids are sebacic and azelaic or mixtures thereof.

Minor amounts of adipic used with a major amount of sebacic may also be used with advantage.

Various; useful ester base .oils are disclosed'in US. "Patents Nos. 2,499,983,: 2,499,984, 2,575,195, 2,575,196,

2,703,811,11 2,705,724 and 2,723,286.. Generally, the; synthetic base oils consist essentially or carbon, hydro-, gen and oxygen, i.e., the essential. Lnuclear, chemical However,

these oilsimay be substituted with other elements such as halogens, eIg., chlorinelandlflnorineuf Some representm, tive componentsuof ester lubricants are ethyl p-alrnitate, ethyl stearate, di-(Z-ethylhexyl) sebacate, ethylene glycol f di-laurate, di-(Z-ethylhexyl) phthalate, di-(l,3-rnethyl butyl) 'adipate, di-(Z-ethyl butyl) adipate, di-f(1-eth-yl structure is formed by these elements alone.

propyl); adipate, diethyl .oxylate, gly'ceroLtri-n-octoate, di-

cyclohexyl radipate, .di-(undecyl) sebacate,..tetraethylene glycol-di-(Z-ethylene hexoate); di-Cellosolve phthalate, butyl phthallyl butyl glycolate, di-n-hexyl furnarate .polymer, dibenzyl, sebacate,; and .diethylene glycol bis: (2-nbutoxy ethyl carbonate). 2-ethylhexyl-adipaterneopentyl .glycyl-adipate-2-ethylhexyl, is a representative complex Generally, these.v synthetic ester lubricants have' a viscosity ranging. fromlight to heavyoils; 'e.g about:50

ester.

Particularly. suitable ester base oils are formed; when .these alcohols" are reacted with, monocanboxyli'c acids having about 5 to 12 'carbonatoms, preferably ;4 to i 9 carbon atoms. It is preferred thatfrhe reaction -be con- SUS at 100 F. to 250 SUS at 210 F., and preferably 30 to 150 SUS at 210 F.

The esters are manufactured, in general, by mere reaction of the alcoholic and acidic constituents, although simple esters may be converted to longer chain components by transesterification. The constituents, in the proportions suitable for giving the desired ester, are reacted preferably in the presence of a catalyst and solvent or Water entraining agent to insure maintenance of the liquid state during the reaction. Aromatic hydrocarbons such as xylene or toluene have proven satisfactory as solvents. The choice of solvent influences the choice of temperature at which the esterification is conducted; for instance, when toluene is used, a temperature of 140 C. is recommended; with xylene, temperatures up to about 195 C. may be used. To provide a better reaction rate an acid esterification catalyst is often used. Many of these catalysts are known and include, for instance, HCl, H 80 NaHSO aliphatic and aromatic sulfonic acids, phosphoric acid, hydrobromic acid, HF and dihydroxyfiuoboric acid. Other catalysts are thionyl chloride, boron tri-fluoride and silicon tetrafluoride. Titanium esters also make valuable esterification and transesterification catalysts.

In a preferred reaction, about 0.5 to about 1 weight percent, or advantageously, 0.2 to 0.5% of the catalyst is used with a xylene solvent at a temperature of 165 to 200 C. while refluxing water. The temperatures of the reaction must be sufficient to remove the water from the esterification mass as it is formed. This temperature is usually at least about 140 C. but not so high as to decompose the wanted product. The highest temperature needed for the reaction will probably be about 200 C.,

preferably not over about 175 C. The pressure is con- 9 veniently about atmospheric. Although reduced pressure or superatmospheric pressure could be utilized, there is usually no necessity to use reduced pressures, as the temperatures required at atmospheric pressure to remove the water formed do not usually unduly degrade the product.

When reacting gylcols with dibasic acids to produce a polyester, it is preferred to continue the reaction with concomitant boiling off of water from the reaction mixture until the polyester product has a kinematic viscosity of about 15 to 200 centistokes at 210 F., preferably about 40 to 130 centistokes. When this point has been reached, the polymerization can be stopped, for instance, by adding a capping alcohol to the reaction mixture, and continuing to reflux until Water ceases to be evolved. The capping alcohol is a low molecular weight monoalcohol of up to about 20 carbon atoms. It is standard practice, when esters are made using the conventional acid catalysts such as sodium bisulfate or paratoluenesulfonic acid to give the esters an after-treat by washing the ester with a 5 percent aqueous K CO solution or by heating the ester in an autoclave for 15 hours at 340 to 350 F. with 10 weight percent of propylene oxide. It is also conventional to subject the ester to filtration to remove insoluble materials. After this the product may be subjected to a reduced pressure distillation or stripping at 100 to 200 C. to remove volatile materials, such as water, the solvent and light ends.

If desired, other additives may be added to the synthetic lubricant com-positions of the present invention to improve other characteristics of the lubricant so long as they do not deleteriously affect the functional properties of the composition. Such additives are for instance, anti-oxidants, viscosity index improvers, corrosion inhibitors, other extreme pressure agents, etc.

The following examples are included to further illustrate the reaction products of the present invention and the properties of lubricants containing them but are not to be considered limiting.

Example I Example II Di-(l-chloroethyl) chlorendate was prepared by reacting 185 grams (0.5 mole) of chlorendic anhydride and grams (1.12 mole) of ethylene chlorohydrin in toluene solvent using about 0.3 gram of toluene sulfonic acid as catalyst. After 9.5 ml. of water had been recovered from the reaction (106% of theory), the solvent and any unreacted ethylene chlorohydrin was removed under vacuum. The product had a chlorine analysis of 54.1 (theoretical 55.5). Product G.

Oil blends of Plexol 201-] (di-2-ethyl hexyl sebacate) and various concentrations of the polyester of Example I were prepared and tested for load carrying ability in the Falex lubricant testing apparatus and the SAE Extreme Pressure Testing Machine. Plexol 201-] without the polyester was also tested. The results are shown in Table I below.

For comparative purposes the various concentrations of the diesters of Examples HI to V below in Phexol 201-] were also tested.

Example III Dibutyl chlorendate was prepared by refluxing 371 grams (1 mole) of chlorendic anhyride, 300 grams of nbutyl alcohol (4 moles) and 2.5 grams of ptoluene sulfonic acid, until the theoretical amount of water (18 ml.) had been collected in a water trap. The excess water was then removed under vacuum to a pot temperature of C. The product was designated Product D and analyzed 42% chlorine (theoretical 42.5%).

Example IV A product was prepared from dry lauryl alcohol and chlorendic anhydride, using paratoluene sulfonic acid as a catalyst. Toluene was used to entrain water of reac tion. After theoretical water had been derived from the reaction, butyl alcohol was added and the reaction continued. The final product was Washed with dilute NaOH and Water and topped to 150 C./11 mm. The product was designated Product H and analyzed 27.8% chlorine (theoretical 29.4).

Example V Dioleyl chlorendate was prepared by refluxing in toluene solution 93 grams of chlorendic anhydride (0.25 mole), 150 grams of oleyl alcohol (0.5 mole) and 3 grams of toluene sulfonic acid until the theoretical amount of water (4.5 ml.) had been collected in a water trap. After removal of the toluene solvent and cooling to room temperature, 18 grams of sulfur (0.56 mole) were added and the reaction mixture maintained at -185 C. with constant stirring for 8 hours. The product, after filtering through Super Cel, had a chlorine analysis of 21.2% (theoretical 20.2) and a sulfur analysis of 6.21% (theoretical 7.0). Product E.

The data of Table I demonstrates the improved load carrying capacity of synthetic lubricants containing the diesters of the present invention when compared to the load carrying capacities of the synthetic oil alone. With respect to the other diesters tested the results show that while the SAE load value of lubricants containing these additives is comparable to the SAE load values provided wherein i s'an aliphatic hydrocarbon-radical of 8 to 1 6 by the additives of the present invention, the Fale'X Test carbon atoms. 7 valuesare far inferior. 2. T he composition of claim I wherein R is an aliphatic hydrocarbon radical of 10 110 14 carbon-atoms.

TABLE I Falex (lbs) Additive Reactants Class Cone. SAE safe percent a load (lbsz) Pass Fail F Lauryl mercaptan plus chlorendic acid Diester V 0.5 1, 750 2,000 335 V 2.0 4, 500+ None 388 G Ethylene chlorohydrin plus chlorendic acid-.- lo 0. 5 4, 500+ None 386 r 2.0 491 3. 450+ Butyl alcohol plus clllorcudic acid d0 0.5 1,500 1, 750 328 a 2. 0 1,500 1, 750 ass 3.0 436 Lauryl alcohol plus chlorendic acid d0; 0. 1,250 1, 500 363 2. 0 1, 250 1, 500 385 Oleyl alcohol plus ehlorendic acid plus S ."do 0.5 1, 250 1,500 275 1 8 4, 500+ None a In Plexol 201-.T which is di-2-ethyl hexyl sebacate plus sebacic acid (free).

It isfclaimedi References Cited :by the Examiner 1. A lubricant composition consisting essentially of an UNIT D PATENTS ester-based fluid of lubricatingvis'cosity, said ester-based S ES fluid being of an alkanol of 4 to 12 carbon atoms and an 5 7/1944 Plruttoin 4 alkane carboxylic acid of 4 to 12 carbon atoms, and a 2 ,733,248 1/ 1956: Lidov 252-545 X. minor amount suflicient to improve the load carrying 2 771 423 11 195 Dorinson 252 54 "Tapacity; measured by Falex E m s. 2,938,870 5/1960 Dorinson -4- 252'48';4 Test, of said fluid, of a base oil-compatible drester having V the structural formula: 9 2 1/1961 Donnson 252*48'4 H 3,072,571 1/1963 Jordan et a1 252 -545 X1 1 l .1 V DANIELE. WYMAN', Primary Examinr.

I i JULIUS GREENWALD, Examiner. V ClCC-C-C-SR l 1| C1 H O 

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF AN ESTER-BASED FLUID OF LUBRICATING VISCOSITY, SAID ESTER-BASED FLUID BEING OF AN ALKANOL OF 4 TO 12 CARBON ATOMS AND AN ALKANE CARBOXYLIC ACID OF 4 TO 12 CARBON ATOMS, AND A MINOR AMOUNT SUFFICIENT TO IMPROVE THE LOAD CARRYING CAPACITY AS MEASURED BY THE FALEX EXTREME PRESSURE TEST, OF SAID FLUID, OF A BASE OIL-COMPATIBLE DIESTER HAVING THE STRUCTURAL FORMULA: 